1. Field of the Invention
The present invention relates to a two-dimensional solid-state image sensor which is equipped with an image processing function.
2. Description of the Prior Art
An image picked up by a two-dimensional solid-state image sensor is an assembly of discrete image information spatially sampled in two dimensions. In the prior art, the image data is subjected to two-dimensional image processing for improvement of image quality and for other purposes.
FIG. 1 is a block diagram showing a prior art example involving such image processing. In this case, two-dimensional image processing for increasing the sharpness of image, removal of noise and so forth is performed by conducting a convolution of each image data f(x, y) from a photoelectric converter or optoelectro transducer unit 100 and a predetermined two-dimensional weight function.
In FIG. 1, the photoelectric converter 100 has image sensor cells P.sub.11 to P.sub.mn arranged in a matrix form and the picture element cells are formed, for example, by CCDs, BBDs or the like. Accordingly, image information G.sub.11 to G.sub.mn of the image sensor cells P.sub.11 to P.sub.mn are read out only in the form of a one-dimensional time series signal. In the prior art, as shown in FIG. 1, the read-out signal is delayed by delay circuits 101 and 102 to obtain image information G.sub.i,j-1, G.sub.i,j and G.sub.i,j+1 of the same timing, which are multiplied by predetermined constants .alpha..sub.1 to .alpha..sub.3 in multipliers 103 to 105, respectively, and the multiplied outputs are added together by an adder 106, thus performing one-dimensional image processing first. Since the photoelectric conversion elements or optoelectro transducers, such as the CCDs and BBDs, are the destructive readout type, the result of the abovesaid operation is once loaded in digital form in a buffer memory 107 which has memory areas P'.sub.11 to P'.sub.mn respectively corresponding to the image sensor cells of the photoelectric converter 100. Then, the contents of the buffer memory 107 are read out therefrom in a direction perpendicular to the direction of readout of the photoelectric converter 100. The output from the buffer memory 107 is subjected to the same operation as the aforesaid one by a circuit composed of delay circuits 108 and 109, multipliers 110 to 112 and an adder 113, thereby performing two-dimensional image processing.
As will be seen from the above, in the case where an image picked up by a two-dimensional solid-state image sensor is subjected to two-dimensional image processing for improvement of image quality as well as image analysis, it is impossible in the prior art to perform the two-dimensional image processing until after signals subjected to the one-dimensional image processing have once been loaded in an external buffer memory of large capacity. Accordingly, the prior art requires a very complex circuit arrangement involving a buffer memory of the capacity corresponding to the image sensor cells and an A-D converter for loading signals in the buffer memory and, further, cells for the provision of the large capacity buffer memory on the outside of the device. Therefore, in the prior art, the image processing function cannot be provided in the solid-state image sensor. Moreover, since signals are subjected to the image processing outside the solid-state image sensor and passed through many circuits, the signals are liable to be affected by noise, presenting a problem in terms of image processing performance, too.